Analog loop filters are utilized to generate signals that are in a precise relationship with a given input signal. Analog loop filters can be used in many applications, including phase locked loops and delay locked loops. Phase locked loops generate output signals that are in a determined phase and frequency relationship with an input signal, while delay locked loops regulate the phase of an input clock signal.
In a phase locked loop, regulation of the phase and frequency is accomplished through a stabilized reference oscillator, such as a voltage controlled oscillator. Delay locked loops, in contrast, do not employ reference oscillators. Instead, delay locked loops employ delay lines in place of reference oscillators to change the phase of a clock signal. Phase locked loops are employed, for example, in radio, telecommunications, computers and other electronic applications for applications like signal recovery, frequency synthesis, or pulse distribution. Delay locked loops are employed, for example, in integrated circuits to change the phase of a clock signal or for clock recovery.